A gray whale's flukes are seen at the San Ignacio Lagoon, Baja California Sur state, Mexico on February 28, 2010. Although a debate is now raging among some whaling nations to begin limited hunting again, the Pacific gray whales have been protected since 1947, and are at the center of a growing whale-sightseeing industry. Their numbers have dropped by a third, from around 26,000, in the late 1990s. Scientists say that the decline was caused by melting artic ice impacting on their food chains, which include small fish, crustaceans, squid and other tiny organisms. A small-scale whale-sightseeing industry was developed in the remote spot of San Ignacio Lagoon, off Mexico's northwest Baja California peninsula, where grey whales breed and nurse their calves each year after migrating thousands of miles from Canada and Alaska. AFP PHOTO/OMAR TORRES ---- MORE PICTURES IN IMAGE FORUM (Photo credit should read OMAR TORRES/AFP/Getty Images) less

A gray whale's flukes are seen at the San Ignacio Lagoon, Baja California Sur state, Mexico on February 28, 2010. Although a debate is now raging among some whaling nations to begin limited hunting again, the ... more

Photo: Omar Torres, AFP/Getty Images

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A grey whale calf exhales through its blowholes at the San Ignacio Lagoon, Baja California Sur state, Mexico on March 1, 2010. Although a debate is now raging among some whaling nations to begin limited hunting again, the Pacific gray whales have been protected since 1947, and are at the center of a growing whale-sightseeing industry. Their numbers have dropped by a third, from around 26,000, in the late 1990s. Scientists say that the decline was caused by melting artic ice impacting on their food chains, which include small fish, crustaceans, squid and other tiny organisms. A small-scale whale-sightseeing industry was developed in the remote spot of San Ignacio Lagoon, off Mexico's northwest Baja California peninsula, where grey whales breed and nurse their calves each year after migrating thousands of miles from Canada and Alaska. AFP PHOTO/OMAR TORRES (Photo credit should read OMAR TORRES/AFP/Getty Images) less

A grey whale calf exhales through its blowholes at the San Ignacio Lagoon, Baja California Sur state, Mexico on March 1, 2010. Although a debate is now raging among some whaling nations to begin limited hunting ... more

Photo: Omar Torres, AFP/Getty Images

Image 3 of 3

Gray whales - a study in climate change survival

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The massive gray whales that migrate each year between Alaska's Bering Sea and Baja California have survived thousands of years of sea level and climate change by altering the way they live and feed, UC Berkeley scientists have found.

And those major adaptations, they say, could put them in good position to withstand climate change taking place today.

Long before now, the scientists said - perhaps 2 million years ago or more - evolution shaped gray whales' skulls, allowing them to find food in two very different ways.

Today, they can dive to the ocean bottom and suck up the muddy sediments that their whisker-like baleen will filter out to get tons of nutritious worms and tiny crustaceans - as much as 900 pounds a day. Or they can swim through the open water with mouths agape to filter out masses of krill, herring and other small fish.

One small group of gray whales along the North Pacific coast no longer migrates to the Bering Sea from Baja each year nor forages for food in the ocean sediments off Alaska.

Instead, those whales remain year round near Vancouver Island in Canada and off the tiny Humboldt County town of Trinidad, a onetime whaling center. They use what the scientists call a "diverse set of feeding modes" that has turned them into hunters of the open ocean - like their relatives, the blue whales and the humpbacks.

It's a behavioral change that has occurred since the last ice age ended some 10,000 years ago and sea levels rose, and that the evolution of their skulls made possible so long ago.

David Lindberg, an evolutionary biologist at Berkeley, and Nicholas Pyenson, a former Berkeley graduate student and now curator of fossil marine mammals at the Smithsonian Institution in Washington, used the many cycles of past climate and sea level changes to study the whales' survival patterns.

Their study is published in the current issue of the online journal PLoS One.

The scientists focused on the changes in sea levels that occurred between 120,000 years and 10,000 years ago. In that period, glaciers and ice sheets alternately advanced far south from the Arctic, and retreated again and again as the climate changed.

Diversifying

The oceans also froze and sea levels shrank, then warmed again, and sea levels rose. With those changes came changes in the availability of food. Some whales, including the grays, met those challenges by diversifying their way of life, the scientists have found.

Lindberg and Pyenson estimate that long before the arrival of humans on the West Coast, gray whales throughout the North Pacific could have numbered as high as 120,000. But commercial whaling began about 1845, continued into the early 20th century and killed off thousands of whales of virtually every species.

Rigorous protection since then has restored gray whale numbers to about 22,000, Lindberg and Pyenson estimate, and as climate change continues and the water of the North Pacific Ocean warms, the "plasticity" of the gray whales - their ability to find food in diverse ways - should give them a distinct advantage, they say.

"I suspect the gray whales will be among the winners in the great climate change experiment," Pyenson said.